using System;
using System.Threading;
using System.Threading.Tasks;

using VNLib.Utils.Logging;

namespace VNLib.Plugins.Extensions.Loading.Events
{

    /// <summary>
    /// A deletage to form a method signature for shedulable interval callbacks
    /// </summary>
    /// <param name="log">The plugin's default log provider</param>
    /// <param name="pluginExitToken">The plugin's exit token</param>
    /// <returns>A task the represents the asynchronous work</returns>
    public delegate Task AsyncSchedulableCallback(ILogProvider log, CancellationToken pluginExitToken);

    /// <summary>
    /// Provides event schedueling extensions for plugins
    /// </summary>
    public static class EventManagment
    {
        /// <summary>
        /// Schedules an asynchronous event interval for the current plugin, that is active until canceled or until the plugin unloads
        /// </summary>
        /// <param name="plugin"></param>
        /// <param name="asyncCallback">An asyncrhonous callback method.</param>
        /// <param name="interval">The event interval</param>
        /// <returns>An <see cref="EventHandle"/> that can manage the interval state</returns>
        /// <exception cref="ObjectDisposedException"></exception>
        /// <remarks>If exceptions are raised during callback execution, they are written to the plugin's default log provider</remarks>
        public static EventHandle ScheduleInterval(this PluginBase plugin, AsyncSchedulableCallback asyncCallback, TimeSpan interval)
        {
            plugin.ThrowIfUnloaded();
            
            plugin.Log.Verbose("Interval for {t} scheduled", interval);
            //Load new event handler
            return new(asyncCallback, interval, plugin);
        }
        /// <summary>
        /// Registers an <see cref="IIntervalScheduleable"/> type's event handler for 
        /// raising timed interval events
        /// </summary>
        /// <param name="plugin"></param>
        /// <param name="scheduleable">The instance to schedule for timeouts</param>
        /// <param name="interval">The timeout interval</param>
        /// <returns>An <see cref="EventHandle"/> that can manage the interval state</returns>
        /// <exception cref="ObjectDisposedException"></exception>
        /// <remarks>If exceptions are raised during callback execution, they are written to the plugin's default log provider</remarks>
        public static EventHandle ScheduleInterval(this PluginBase plugin, IIntervalScheduleable scheduleable, TimeSpan interval) => 
            ScheduleInterval(plugin, scheduleable.OnIntervalAsync, interval);
    }
}